1. Field of the Invention
The present invention relates to an image forming device and an image forming method which form an image by ejecting ink drops and reaction liquid drops which react with the ink drops.
2. Description of the Related Art
Inkjet printers, which are equipped with a recording head at which a plurality of nozzles which eject liquid drops are arranged, and which carry out recording of an image by ejecting ink drops from the nozzles, are currently coming into wide use.
In recent years, in order to improve the image density and in order to overcome the spreading of inks into the sheet and the blurring between colors which arises at portions where different colors contact one another, inkjet printers have employed a method of applying onto a sheet, in addition to the inks of the respective colors, a reaction liquid which reacts with the inks (a printability improving liquid which causes the coloring materials within the inks to cohere, thicken, or become insoluble).
When using a reaction liquid, if the amount of the reaction liquid is too large, problems arise in that the total amount of moisture which the sheet absorbs is large and wrinkles form in the sheet, or the reaction liquid goes to waste when it is ejected at unneeded regions on the sheet.
Thus, various techniques have conventionally been proposed in order to eject an appropriate amount of reaction liquid at a desired position.
For example, there has been proposed an inkjet printing device which generates data for ejecting reaction liquid (synonymous with processing liquid) by computing the logical sum of ink ejecting data (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 08-281932).
There have also been proposed an inkjet recording device which assigns reaction liquid data, by using a dither pattern, from data for the ink after halftone processing (see, for example, JP-A No. 11-334114), and an inkjet recording device which carries out thinning of respective density ink data by using a mask and generates reaction liquid data by computing the logical sum of the mask pattern and the reaction liquid data after thinning, thereby making the amounts of reaction liquid to be ejected differ in accordance with the amount of or the type of the coloring material of each ink to be ejected from a recording head onto a recording material (see, for example, JP-A No. 2002-321349). Further, there is also known an inkjet recording device which, when the image density is less than or equal to a predetermined density, generates data for a reaction liquid which is for applying reaction liquid to the same place as the place to which ink is applied on the basis of data for the ink, and, when the image density is greater than the predetermined density, generates data for a reaction liquid so as to apply reaction liquid to places from which are thinned out places where ink is applied on the basis of the data for the ink (see, for example, JP-A No. 11-309882).
An inkjet recording method, which applies reaction liquid when the ink duty is greater than or equal to a predetermined value and which does not apply reaction liquid when the ink duty is less than or equal to the predetermined value, also is known (see, for example, JP-A No. 2005-007649). In this inkjet recording method, reaction liquid data is generated by error diffusion, without relation to the ink data.
However, in an inkjet printing device such as proposed in JP-A No. 08-281932, there is the problem that fine control with respect to the ink amount cannot be carried out merely by computing the logical sum.
Further, in inkjet recording devices such as proposed in JP-A Nos. 11-334114, 2002-321349, and 11-309882, the reaction liquid data generating pixels depend on the mask (the dither pattern). Therefore, there is the problem that bias arises in generating the reaction liquid data, depending on the relationship between the ink data and the mask. Further, the reaction liquid amount cannot be freely adjusted merely by thinning by using the dither pattern. In addition, such methods cannot address cases in which it is desired to change the amount of the reaction liquid at the first color or the second color.
In an inkjet recording method such as proposed in JP-A No. 2005-007649, because the reaction liquid data is generated by error diffusion and without relation to the ink data, there are cases in which reaction liquid which is more than needed is applied even to regions where the application of reaction liquid is not necessary or only a small amount thereof suffices, such as regions in which ink drops are not formed, low density regions, or the like. Accordingly, the reaction liquid is consumed wastefully.